Simple libc-based RTC test

Issue #3450

repos/libports/run/system_rtc.run

@@ -9,7 +9,7 @@ if {[expr ![have_include power_on/qemu]]} {
 
 set build_components {
 	core init timer drivers/rtc server/system_rtc test/system_rtc
-	server/report_rom
+	server/report_rom test/libc_rtc
 }
 
 build $build_components
@@ -83,6 +83,20 @@ set config {
 			<any-service> <parent/> </any-service>
 		</route>
 	</start>
+
+	<start name="test-libc_rtc" caps="150">
+		<resource name="RAM" quantum="4M"/>
+		<config>
+			<vfs> <dir name="dev"> <log/> <rtc/> </dir> </vfs>
+			<libc stdout="/dev/log" stderr="/dev/log" rtc="/dev/rtc"/>
+		</config>
+		<route>
+			<service name="Rtc"> <child name="system_rtc"/> </service>
+			<service name="Timer"> <child name="timer"/> </service>
+			<any-service> <parent/> </any-service>
+		</route>
+	</start>
+
 </config>}
 
 install_config $config
@@ -90,6 +104,7 @@ install_config $config
 set boot_components {
 	core ld.lib.so init timer rtc_drv test-system_rtc system_rtc
 	report_rom
+	test-libc_rtc libc.lib.so libm.lib.so posix.lib.so vfs.lib.so
 }
 
 build_boot_image $boot_components

repos/libports/src/test/libc_rtc/main.cc

@@ -0,0 +1,46 @@
+/*
+ * \brief  Simple libc-based RTC test using clock_gettime()
+ * \author Martin Stein
+ * \date   2019-08-13
+ */
+
+/*
+ * Copyright (C) 2019 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#include <stdio.h>
+
+#include <unistd.h>
+#include <time.h>
+
+int main()
+{
+	unsigned idx = 1;
+	while (1) {
+		struct timespec ts;
+		if (clock_gettime(0, &ts)) {
+			return -1;
+		}
+
+		struct tm *tm = localtime((time_t*)&ts.tv_sec);
+		if (!tm) {
+			return -1;
+		}
+
+		printf("Timestamp #%d: %d-%d-%d %d:%d %ds\n",
+			idx++,
+			1900 + tm->tm_year,
+			1 + tm->tm_mon,
+			tm->tm_mday,
+			tm->tm_hour,
+			tm->tm_min,
+			tm->tm_sec);
+
+		sleep(1);
+	}
+
+	return 0;
+}

repos/libports/src/test/libc_rtc/target.mk

@@ -0,0 +1,7 @@
+TARGET = test-libc_rtc
+LIBS   = posix
+SRC_CC = main.cc
+
+vpath main.cc $(PRG_DIR)
+
+CC_CXX_WARN_STRICT =